Good morning. It's really a great honor for me to introduce this year's Thomas Starzl State of the Art speaker, Professor Peter Friend. Peter Friend obtained his medical degree from the University of Cambridge, and after a short stint at Indiana University where he began the liver transplant program there, he returned to the UK in 1989 to the University of Cambridge. In 1999, he went to the University of Oxford where he continued to rise in prominence. He's currently the professor of transplantation at the University of Oxford and director of the Oxford Transplant Center. He's chairman of the Multivisceral and Composite Tissue Advisory Group to the NHSBT and a past president of the British Transplantation Society. He is the Royal College of Surgeons National Specialist Lead for Transplantation Research and was recently awarded a Lifetime Achievement Award by the British Transplantation Society for his career-spanning work in the field of organ transplantation. A special note for this lecture, Peter is co-founder and chief medical officer of Organox and has spent over 20 years on the development of normal thermic organ perfusion technology. Professor Friend leads the preclinical and clinical programs of Organox's patent in normal thermic organ perfusion technology, which as we all know has really become front and center in the recent years. And it really is a pleasure now to welcome Professor Friend as this year's Thomas Starzl State of the Art Lecturer. Thank you. Well we can wait. Dr Olsdottir, thank you very much indeed for that introduction. It's a huge pleasure to to be able to deliver this lecture. The invitation for this lecture means a great deal. I was lucky enough to be able to visit Pittsburgh in the late 1980s and to experience just what an extraordinary place it was under Thomas Stasel's leadership and just what an extraordinary and inspirational man he was. So thank you very much for the honor of giving this named lecture on the topic of normothermic liver perfusion. You have heard that I have a disclosure which is my relationship with organox. Well liver graft perfusion is not new. In fact Dr Stasel got there first. This publication of his in 1968 describes his hypothermic oxygenated perfusion system which he used in his early liver transplants. But this technology was rapidly supplanted by the then emerging specialist cold preservation solutions. But now it's come back. So what is the problem that machine perfusion is the solution to? There are a number of devices either in clinical trials or in commercial sales which all aim to improve the quality of donor organs. The problem is this is the supply as we as we all know. If we take a snapshot and look at what happened to patients who are listed for liver transplantation in the year 2017 in this country and see what happened what had happened to them three years later only 58 percent had received a transplant. 33 percent had died or been removed from the list mostly because they were too sick to remain and nine percent were still waiting. In 2020 there were twelve and a half thousand eligible donors and only eight and a half thousand liver transplants. That gives a utilization rate of 67 percent. So utilization of some of those untransplanted organs becomes a very key and vital challenge to us. In this context the icebox although effective for many decades is now a rate limiting step. Cooling organs down is not good for them. Lack of oxygen is a problem. Anaerobic metabolism leads to the accumulation of metabolites which then form substrates for ischemia reperfusion and because the organ is not functioning we can't measure its viability in order to decide whether it should be transplanted. So this technology was fine for standard criteria donor organs but not for the extended criteria organs that everyone is now having to consider. So we need new preservation technology because of increasing demand because of waiting list mortality because of higher risk donor organs and because of poor utilization. The challenge is to transplant more of these declined high risk organs without compromising the rather excellent outcomes. So what specifically do we want machine perfusion to do? We want it to improve the quality of preservation and to increase its duration. We want it to repair organs from graft injury mostly sustained during the process of death and retrieval. We want to be able to assess organs which will enable us to utilize viable organs rather than decline them and ideally we would like to be able to modify the organ to make it more suitable for the transplant recipient. So let's start first of all with the question of temperature hypothermic or normothermic. There is evidence that both are beneficial and I would point out that it's not actually a binary it's a continuous variable. We tend to think of it however as either cold or warm. So starting briefly with cold the pioneer in this area was James Guerrero who published this paper in 2010 which was the first demonstration that a relatively simple cold machine perfusion system was effective and could be used safely to perfuse organs for six hours. We now know more than we did about what's going on during cold ischemia and this important publication from the group of Michael Murphy and colleagues in Cambridge UK demonstrates the importance of succinate accumulation. Succinate accumulation is that it's a signature a universal signature of ischemic tissue we see it in ischemic myocardium ischemic skeletal muscle and we see it in transplant organs waiting to be transplanted and the problem is that succinate accumulates under the influence of anaerobic metabolism but when oxygen is re-provided that succinate drives the process the it's rapidly metabolized the electron chain is driven effectively in reverse leading to the release of reactive oxygen species at complex one and the important the really important contribution of Murphy and colleagues was to recognize that oxygen prevents that from happening and it prevents it from happening at any temperature. It is not temperature dependent so it's still working in the cold and this was the this was the the effect which was exploited by a number of groups particularly that of the Zurich group of Pierre Clavier and Filip Dukovsky also the group of Robert Porter in Groningen in the Netherlands demonstrating that a relatively relatively short period of machine perfusion at cold temperatures with oxygen had remarkable results in terms of post-transplant outcomes even following a period of quite of quite prolonged cold storage reduction in ischemic cholangiopathy improved graft survival reduced acute rejection rate and that's now that's now been formalized in terms of evidence by this recent publication from the group of Robert Porter in Groningen who randomized 160 DCD livers and demonstrated a a significant both clinically and statistically significant reduction in the instance of clinical ischemic cholangiopathy. Ischemic cholangiopathy is I'm sure most most members of the audience will know is the sort of heart sink of a DCD liver transplantation. It's a it's a fibrotic multi-stricture intra-hepatic problem which often leads to the need for re-transplantations. This is an important result. They also demonstrated a reduction in early allograft dysfunction that's an injury marker a reduction in post-reperfusion syndrome that's the the cardiovascular collapse syndrome which occurs when when high when poor quality organs are re-perfused but demonstrated also no difference in utilization. So onto normothermic machine perfusion which is really the topic of my talk. This recreates physiology. It's quite different from cold storage delivering oxygen maintaining physiological temperature providing nutrients to allow normal metabolic activity to continue during the period of preservation. This abrogates ischemia reperfusion. It allows viability assessment because we can measure organ function. It allows normal cellular recovery processes to take place particularly from hypoxia and because the organ is functioning it opens the opportunity for treating that organ with therapeutic interventions. Well the liver normothermic machine perfusion is now approved in the USA with two FDA approved devices and the question we ask is what is the evidence of benefit? And the first study to be published was this one this European multi-center study published four years ago which is comparing directly normothermic perfusion with static cold storage in the icebox. The primary endpoint was an acute injury marker the the maximum level of transaminase in the first week. This is a validated surrogate marker for graft survival and it showed a 49% reduction. The trial also showed reduction of early allograft dysfunction a reduction in non-anastomotic bilirestrictors in the DCD cohort and a clinically important reduction in the post reperfusion syndrome. This was despite a 54% average average increase in the preservation time and a 20% increase in organ utilization. The second study to be published was from the transmedics IDE study published at the beginning of this year. This is a very similar study it also showed a marked reduction a significant reduction in graft injury ischemia reperfusion as measured by early allograft dysfunction. It showed benefits with respect to ischemia reperfusion markers of histology to ischemic biliary complications to post reperfusion lactate and also to the utilization of DCD organs. So all very positive results. And the third study which is the organox multi-center IDE study similar design again primary endpoint early allograft dysfunction a smaller reduction but a greater reduction in the higher risk cohorts particularly the DCD cohort and the top quartile of donor risk index organs where the difference was really marked and clinically important. Again reduction in post reperfusion syndrome an increase in the average preservation time but no difference in biliary complications or utilization. So the two organox based studies have been subjected to a pooled data propensity score analysis and that of course brings up the numbers and there are co-primary endpoints of early allograft dysfunction and PKST and they both show exactly the same thing as you might imagine with a marked reduction in early graft injury markers. So to summarize the three randomized controlled clinical trials to date there is good evidence now for reduction in acute liver injury for reduction in post reperfusion syndrome which is very important when transplanting sick patients for increased duration of preservation for viability assessment and some evidence for improved organ utilization. But I would stress that randomized clinical trials are not particularly well suited in fact they're poorly suited to comparing technologies that make different claims. It's difficult to persuade a clinician to randomize a patient into a clinical trial if they wouldn't have accepted it for the standard of care icebox. It's a fundamental limitation in the randomization process. So that's why it's important to look at studies where randomization has not taken place to see what the evidence is that we can push the boundaries out and there are two important studies published one from Birmingham in the UK and one from the Cleveland Clinic and I'm putting them up together because they are very similar. They both recruited livers which have been declined in the case of the Birmingham study by all the UK liver transplant units. They both recruited livers that have been declined for similar reasons as you can see here and they both involved assessing the quality of the organ on perfusion in one case at four hours and the other at six hours and they both transplanted 71 percent of those livers as a result of those viability assessments. These trials were conducted completely independently so I think it's very striking that the results are so similar. So we have evidence therefore that normothermic machine perfusion does have beneficial effects in terms of organ utilization. So two of the three studies I've just presented randomized studies I've just presented and both the single arm studies I've just presented provide really quite good corroborating evidence of improved utilization although it was not the primary objective of the randomized trials of course. In contrast the two published studies of oxygenated hypothermic machine perfusion although demonstrating benefits do not demonstrate any difference in utilization and I think the reason for this is that there is much less evidence available from oxygenated hypothermic machine perfusion in terms of functional testing and so what this means is that by and large this is beneficial to organs that are already going to be transplanted. But the jury is still out to some extent so we are conducting a multi-center study in the UK in fact all the UK liver transplant centers are collaborating on this to look at the effect of the availability of normothermic liver perfusion on organs most likely to be declined and to decide what we mean by declined organs we've analyzed three years worth of national data to come up with an algorithm which predicts the risk of non-utilization of decline in other words and we've gone for what's called a threshold crossing trial design the reason being that for good reasons investigators were unwilling to randomize high-risk organs all the transplant units in the UK use some form of machine perfusion for high-risk organs. So we recruit prospectively into the normothermic cohort, the ones in which normothermic perfusion is made available, and we recruit retrospectively according to exactly the same criteria to gain a control group, and we have a predefined target threshold. In other words, we need to know what we mean by a clinically meaningful effect, and the trial has got to exceed that, as it were. The primary endpoint is functional utilization, by which we mean an offer which leads to a transplanted organ which survives for at least a year. And there's an important secondary endpoint, which is the health economic analysis. So let's move on to look at the specifics of DCD liver transplantation in the context of normothermic perfusion. There's no doubt that normothermic perfusion does alter the limits of DCD liver transplantation. This is one case, one anecdote, if you like, from the European trial. It was a high-risk donor, 72 years old DCD. That would have been turned down by a lot of transplant centers. Functional warm ischemia time of 35 minutes. Again, high risk would have been turned down by many, but the lactate cleared from 11 to 0.7 inside one hour. The total preservation time was long, and it was long for logistic reasons. There were other operations in the operating room. So this organ was actually transplanted at 20 and a half hours of total preservation. The reason why that surgeon accepted that organ with such a lot of adverse factors, if you like, is shown in the middle picture, where at 15, almost 16 hours of normal preservation, the liver had a pH of 7.32 and had produced 14 mils of bile in the previous hour, and it was a liver that went on to be transplanted successfully. So coming back to the utilization issue, the European trial in particular demonstrated a 50% difference in utilization of DCD organs. So these are organs in which the DCD donor has proceeded. The organs have been retrieved, but the question is whether they are transplanted, and the transplant rate went up from 55% to 82%. The big issue, and I referred to this earlier on in relation to the cold perfusion paper, is ischemic langiopathy, often referred to as the Achilles heel of DCD liver transplantation. The European trial uniquely was included in its protocol MRCP evaluation at six months in order to get an objective view as to what was happening with the biliary tree, and what we saw was a reduction in the instance of MRCP-diagnosed ischemic langiopathy from 26% to 11%. Now, notably, there was only one liver in each arm which had to be re-transplanted, so the MRCP may be over-calling somewhat, but that's an important difference. You will see that that is not statistically significant. The reason for that is almost certainly because the trial was not powered against this particular endpoint, and we committed a cardinal error with this trial, which is that we allowed statistics to be carried out on secondary endpoints, which you should not do. But we now know more about the biology of DCD, and in this publication looking at a tissue culture and then a transplant model, what happens when cholangiocytes are subjected to DCD conditions, which means warm ischemia followed by cold ischemia, and there is epithelial to mesenchymal transition, which takes about seven days to become manifest, and which can be blocked by treatment with TGF-beta receptor antagonist, and this has been corroborated in an in vivo model with rat liver transplantation. So, I put this out really just to demonstrate that there are things we can do to these at-risk livers. This is a target for intervention which we should perhaps consider very seriously. So, on now to look at viability assessment, which of course is key to organ utilization. Testing is much easier if the liver is working. That stands to reason the clinicians active in the field are looking mainly at metabolic parameters, clearance of lactate, stability of pH, glucose consumption, also bile production, but more importantly bile composition and factor V production and injury markers, but there is a lot of work going on looking at genetic, proteomic, metabolomic, and other biomarkers which may help us refine a much more effective predictive algorithm. This study from Cambridge, where a lot of work has been done on this, demonstrates really moderately good predictive power by looking at the biochemistry of the bile. In particular, the ratio of glucose between the perfusate and the bile seems to be relatively predictive of long-term biliary outcome. So, on to the logistics. What can we do in terms of the benefits of longer preservation? Well, the answer is it could make a big difference. We could schedule multiple transplants. We can test the donor organs more carefully. We can carry out distant retrievals more easily. We can bring patients in from further afield. We can move into daytime operating, and that of course is extremely important for team sustainability. So, the photograph on the left coming from the University of Birmingham in the UK, there were three liver transplants. The livers were all in the operating department at the same time. Two of them were machine perfused. So, operating room scheduling important. Surgical outcomes, there is increasing evidence that complex surgery is better done during the day. However much liver transplant surgeons don't mind operating at night, actually it's something which is probably best avoided. And sustainability of the team, not just the surgeons, is really becoming a key issue. On the right, we see a picture from the intensive care unit at the University of Innsbruck Hospital, where the head there, Stefan Schneeberger, has taken on normothermic machine perfusion with the specific intention of moving to daytime liver transplantation, and that's precisely what he's done. And they recently analyzed their first 59 cases and compared them with propensity score matched controls, and they included in this protocol MRCPs. And the preservation times were much longer in the NMP group, 21 hours versus seven hours, but there was no difference in patient or graft survival. There was no difference in overall biliary complications, and there was a significant reduction in the incidence of ischemic cholangiopathy. So good evidence that we can get longer preservation without compromise. And in the future, multi-day preservation is feasible. These two publications from Pierre Clavian's group in Zurich have demonstrated that by increasing sophistication of the perfusion methodology, including dialysis and better control of carbohydrate metabolism, and a number of other innovations, it's possible to perfuse organs for up to at least a week. And also the first successful transplant at three days of preservation has been recently reported. And this may actually lead on to a more specialized, centralized organ reconditioning type of approach, whereby high-risk organs go to a specialized assessment and repair center where their perfused, assessed, appropriate intervention is delivered, and then if the organs fulfill appropriate release criteria, they go out for transplantation. That's being actively considered in the UK, in Spain, and very much also, I believe, in this country. On to look at evidence of organ repair. There is evidence that simply preserving an organ warm rather than cold is associated with a favorable gene expression. So this publication from the group in King's College Hospital demonstrates normothermic perfused livers, inhibition of pro-inflammatory and expression of regeneration genes, associated also with reduced cellular infiltrates and a reduction in necrosis and apoptosis. But, of course, normothermic perfusion really enables organ-specific interventions. We can be targeting ischemia reperfusion or steatosis. We can be thinking about ways of reducing the immunogenicity of the graft. We can be thinking about ways of dealing with potential microbial transmission. And there are all sorts of delivery approaches, as you can see, drugs, nanoparticles, cells, et cetera. There's a really big future here for therapeutic intervention during prolonged perfusion. And this is just one example. This is what we are doing in Oxford, defatting livers. These are human livers retrieved for transplantation and declined because they're too steatotic. And we're looking at the effect of prolonged machine perfusion, also with the addition of a lipid filter, which you can see in the picture on the bottom center, which is the sort of filter which is used for treating patients with severe congenital familial hyperlipidemia syndromes. And then adding lipid mobilization drugs and regime on the right. And what this demonstrates is that over 48 hours, we can get a lot of fat out of a perfused liver. But quite a lot of the benefit seems to come much earlier than that. So we are just about to start a randomized controlled trial in the UK to test this combined approach of perfusion plus filter plus drug. And gene delivery is more effective at normothermia. This publication from the group of Marcus Seltzner in Toronto demonstrates quite clearly a better uptake of genes. In this case, an oligonucleotide called miravirsin. But the principle is what's important rather than the particular nature of the intervention. And thrombolysis, another big area of interest, particularly in DCD transplants, where there is concern that microvascular thrombosis is part of the problem of morbidity, particularly in the peribiliary vascular plexus. This publication from the Mass General group in looking at discarded human livers showing that it's possible to thrombolyse effectively in terms of measured d-dimer levels and also the histological appearances of the peribiliary vascular plexus. Further in the future, bile duct repair, cultured cholangiocyte organoids. There is a very, very nice publication from the group in Cambridge, UK demonstrating this is when injected into the damaged bile ducts in a mouse model of ischemic cholangiopathy. These can be successfully embedded and become specialized within the native epithelium. And they've even gone on to test the feasibility of this in discarded human livers. So again, very exciting approach to delivering cell therapy. So very briefly to conclude, I want to mention just two topics which are what are called normothermic machine perfusion beyond transplantation or patient connected liver perfusion. The first is liver support and the second is isolated drug delivery. So liver support, this is an old idea, the idea of taking a liver and using it to provide extra corporeal support for a patient in acute liver failure or a patient with acute on chronic liver failure. What we think, however, is that the use of modern perfusion technology may make this a more feasible proposition. So this is the plan with a small device between the perfusion circuit and the patient which exchanges blood between the two. And the second area which we are doing some preliminary work on is isolated in situ hepatic chemo perfusion. This will be for patients with liver cancer confined to the liver. Again, not a new idea, but principle the same that the perfusion technology may make it more feasible. And what we do is to cannulate the liver in situ, this is all being done in a pig model, cannulate in situ portal vein artery IVC, clamp the vessels, place the recipient pig on bypass so the liver is completely isolated, and then deliver a level of chemotherapy which would not be tolerable if given systemically. We've been using Doxorubicin because it's got rapid uptake and it's easy to measure. It could be any drug. And what we demonstrated, however, is that we can achieve tissue levels in the liver which are 10 times higher, as shown in the graph in the bottom row, than would be tolerable systemically. Doxorubicin, of course, is an extremely cardiotoxic drug. And meanwhile, the drug levels in the plasma and in the kidney and in the heart and skeletal muscle were unmeasurable. So to conclude, there is good evidence, I think, for reduced organ injury, improved utilization, longer preservation, and logistic benefits. There is emerging evidence for the way we assess risk, viability assessment, criteria we might use, and there are exciting future prospects for organ-specific interventions. So the concluding observation, if you like, is that normothermic perfusion is a platform to deliver therapies. It is not a destination, necessarily, of itself. And thank you again for the honor of the invitation to speak.

normothermic liver perfusion

liver graft perfusion

organ preservation techniques

physiological temperature

viability assessment

organ repair and modification